The present invention relates to a mobile communication method and system and, more particularly, to call connection of mobile stations.
In a conventional mobile communication system of this type, a unit having a call connection function for mobile stations is connected to a unit of a rank equivalent to that of a transit switch to realize call connection of the mobile stations, as disclosed in "Signaling Architecture in Digital Mobile Communications Network" (THE TRANSACTIONS OF THE INSTITUTE 0F ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS, 1990/11, Vol. J73-B-II, No. 11, pp. 571-584 (to be referred to as reference 1 hereinafter)), "Automatic Pursuit Routing Method in Mobile Communications Network" (THE TRANSACTIONS OF THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS, 1989/5, Vol. J72-B-11, No. 5, pp. 191-200 (to be referred to as reference 2 hereinafter)), and "System and Network Technologies" ("Technologies for Supporting Digital Automobile Telephones", THE TRANSACTIONS OF THE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS, 1990/8, Vol. 73, No. 8, pp. 812-818 (to be referred to as reference 3 hereinafter)).
FIG. 6 shows the network architecture of the conventional digital automobile telephone system disclosed in reference 3. Referring to FIG. 6, reference numeral 1 denotes an ISDN (Integrated Service Digital Network) having zone centers ZC; and 2 and 3, automobile telephone networks for performing call connection of mobile stations MS. Each of the automobile telephone networks is connected to a corresponding zone center ZC and constituted by a gateway mobile communication center (to be referred to as a gateway center hereinafter) G-MCC having gate and transit functions with respect to the ISDN 1, a home memory center HR in which the numbers and visited areas of mobile stations MS are registered, a visited mobile communication center (to be referred to as a visited center hereinafter) V-MCC having visited area management and station connection functions, and a radio base station BS for transmitting/receiving signals to/from the mobile stations MS. Reference numeral 4 denotes a packet network connected to the ISDN 1; 5, an analog telephone network connected to the ISDN 1; and 6 and 7, station telephone sets respectively connected to the analog telephone network and the ISDN 1. Call connection between switching systems such as the gateway centers G-MCC and the visited centers V-MCC is performed by a switching system protocol of the common channel signaling system indicated by the dotted lines in FIG. 6, in which a control signal path is separated from communication paths. According to the terminating protocol disclosed in reference 2, terminating connection to the mobile station MS is performed through the following procedure.
Upon detection of a terminating call to the mobile station MS, the gateway center G-MCC inquiries of the home memory center HR as to the visited center V-MCC which accommodates the visited radio zone of the mobile station MS, and outputs a call set message IAM to the corresponding visited center V-MCC via a public communication network, thereby performing connection to the visited center. This call set message IAM is different from an address signal IAM for call connection in a fixed communication network. In a digital mobile communication network, according to reference 1, the call set message IAM must be a signal corresponding to the following functions:
1. a routing function based on an intra-network routing number (RN), PA1 (2) a retention/transfer function for a terminating dial number, PA1 (3) an inter-node retention/transfer function for mobile station data such as a subscriber class and mobile station class, PA1 (4) a transfer function for intrinsic intra-mobile-communication-network numbers such as a base station number and a radio channel number, and PA1 (5) a backward channel setting function required for any other zone selection/channel switching.
In the above-described conventional mobile communication system, a signal transmitted/received between a center unit equivalent to the visited center V-MCC, in which the mobile station is located, and a center unit equivalent to the gateway center G-MCC based on the conventional techniques and designed to perform connection processing with respect to a commercial public telephone network is unique to the mobile network. For this reason, each of the units equivalent to the visited center V-MCC and the gateway center G-MCC needs to have functions different from those of a unit, i.e., a switching system, used in a public telephone network. Therefore, in order to realize a mobile communication function, a mobile telephone network different from a commercial public telephone network is required.